The present invention relates to voltage comparators, and it is concerned particularly with the use of a voltage comparator under conditions where the voltages being compared differ very little from each other.
There is a growing demand for a comparator, particularly one that can be embodied in MOS (metal-oxide-semiconductor) integrated circuitry, which can reliably detect a voltage difference as small as one millivolt or less within a time period of a few microseconds or less. Prior known MOS comparators have not been designed in a way which is compatible with the stringent requirements just mentioned. Such circuits commonly are designed to sense voltage differences that are an order of magnitude larger than one millivolt in order that they will not be adversely affected by the transient signals which are generated by normal switching or strobing actions within the comparator and the built-in offsets which tend to obscure small input signals. This application presents a new approach to the design of MOS comparators whereby they can respond accurately and reliably to extremely small voltage differences notwithstanding the effects of transients and offsets that are inherent in the circuitry.